A pool check valve is a type of pool valve that provides for one-way water flow, or more importantly, to prevent the flow of water in the opposite direction. Some pool check valves also allow you to monitor the flow of water through a clear lid to ensure proper pool check valve operation. Pool check valves are most commonly used for the following reasons:

• To prevent backflow of water into a spa air blower which will damage the blower's motor.
• For pool pads installed on higher ground or several feet above the pool water level to prevent water from draining back into the pool when the pump is not running.
• To prevent cycling of water in a loop, e.g. solar heater systems.
• To prevent backflow of water from a chlorinator into a heater or filter. This water contains a high concentration of chlorine and can potentially damage the pool heater.